Communications and information technology equipment is commonly designed for mounting to racks and for housing within enclosures (often included in the term “rack”). Equipment racks are used to contain and to arrange communications and information technology equipment, such as servers, CPUs, internetworking equipment and storage devices, in small wiring closets as well as equipment rooms and large data centers. An equipment rack can be an open configuration and can be housed within a rack enclosure, although the enclosure may be included when referring to a rack. A standard rack typically includes front-mounting rails to which multiple units of equipment, such as servers and CPUs, are mounted and stacked vertically within the rack. The equipment capacity of a standard rack relates to the height of the mounting rails. The height is set at a standard increment of 1.75 inches, which is expressed as “U” units or the “U” height capacity of a rack. A typical U height or value of a rack is 42 U, and an exemplary industry standard rack is about six to six-and-a-half feet high, by about 24 inches wide, by about 40 inches deep. A standard rack at any given time can be sparsely or densely populated with a variety of different components as well as with components from different manufacturers.
Most rack-mounted communications and information technology equipment consumes electrical power and generates heat. Heat produced by rack-mounted equipment can have adverse effects on the performance, reliability and useful life of the equipment components. In particular, rack-mounted equipment housed within an enclosure is particularly vulnerable to heat build-up and hot spots produced within the confines of the enclosure during operation. The amount of heat generated by a rack of equipment is dependent on the amount of electrical power drawn by equipment in the rack during operation. Heat output of a rack can vary from a few watts per U of rack capacity up to about 950 watts per U (with this upper end continuing to rise), depending on the number and the type of components mounted to the rack. Also, users of communications and information technology equipment add, remove, and rearrange rack-mounted components as their needs change and new needs develop. The amount of heat a given rack or enclosure can generate, therefore, can vary considerably from a few tens of watts up to about 40,000 watts, and this upper end continues to increase.
Rack-mounted equipment typically cools itself by drawing air along a front side or air inlet side of a rack, drawing air through its components, and subsequently exhausting air from a rear or vent side of the rack. Airflow requirements to provide sufficient air for cooling can vary considerably as a result of different numbers and types of rack-mounted components and different configurations of racks and enclosures.
Equipment rooms and data centers are typically equipped with an air conditioning or cooling system that supplies and circulates cool air to racks. Many air conditioning or cooling systems, such as the system disclosed in U.S. Pat. No. 6,494,050, use an equipment room or data center that has a raised floor construction to facilitate air conditioning and circulation functions. These systems typically use open floor tiles and floor grills or vents to deliver cool air from an air passageway disposed below the raised floor of an equipment room. Open floor tiles and floor grills or vents are typically located in front of equipment racks, and along aisles between rows of racks arranged side-by-side.
The cooling systems and methods that use a raised floor construction typically do not efficiently meet the cooling requirements of rack-mounted equipment. In particular, racks that include high-power equipment having a thermal exhaust air output above 5,000 watts and up to 14,000 watts present a particular challenge for such systems and methods. A raised floor construction typically provides an open floor tile or a floor grill or vent having a venting area of about 12 by 12 inches and is configured to deliver from about 200 cfm to about 500 cfm of cool air. A rack of high-power equipment drawing up to 10,000 watts and requiring an air flow of approximately 1,800 cfm, therefore, would need about 3.5 to about 5 open floor tiles, grills or vents disposed around the rack's perimeter to supply sufficient cool air to meet its cooling requirements, with a 14 kW rack using up to about 2,240 CFM or about 4.5 to about 11.2 floor tiles. Such a floor configuration would be difficult to achieve in equipment rooms crowded with racks, and impossible to implement if racks are arranged side-by-side in rows. Air cooling systems and methods that incorporate raised floor configurations, thus, are typically only used with racks spaced apart to provide sufficient floor area to accommodate multiple open floor tiles, grills or vents. For typical rack spacing, this places a limit on the density of equipment that can be achieved. When a raised floor is not used, distributing cool air from one or more centralized air conditioning systems is even more difficult, as the cool air typically is distributed across a room containing rows of racks.
Equipment rooms and data centers are often reconfigured to meet new and/or different equipment needs that require individual racks to be relocated and/or replaced. In this context, raised floor air cooling systems and methods are inflexible and can typically only be reconfigured and/or retrofitted to service rearranged, relocated and/or newly installed equipment racks at considerable cost. Raised floor configurations cannot easily and inexpensively accommodate the manner by which users typically deploy equipment racks and reconfigure equipment rooms and data centers to meet their new or changing needs.
In addition, cooling systems and methods that use raised floor construction lack physical flexibility and portability to operatively account for a wide variation in electrical power consumption between different racks in an equipment room, and, in particular, between racks and enclosures located in the same row. Cooling systems and methods that rely upon raised floor air passageways and open floor tiles, grills or vents to supply cool air may not be able to easily and inexpensively vary or concentrate cool air to those high power racks that consume relatively large amounts of electrical power and have a high thermal air exhaust output. In addition, newly installed equipment may draw more electrical power than replaced or existing equipment that may lead to thermal problem areas in functioning equipment rooms.
Further, with existing air conditioning solutions, hot spots can develop in a room due to a lack of proper recirculation of exhaust air from racks to the return side of a room air conditioner. This can cause racks to undesirably draw warm air into the racks. To attempt to overcome air circulation problems, many room air conditioners are designed to provide very cool air of approximately 58° F. and receive return air having a typical temperature of approximately 78° F. With an output air temperature of 58° F., it is often necessary to add a humidification system to increase moisture in the air in a data center due to the high level of dehumidification created as a byproduct of over cooling the air. Such humidification systems can be expensive to install and operate.